1. Field of the Invention
The present invention pertains to the art of dishwashers and, more specifically, to spray arm arrangements for dishwashers.
2. Description of the Related Art
Dishwashers are provided with internal spraying devices for directing streams of washing liquid at objects to be washed. More specifically, a dishwasher includes a washing chamber having a bottom sump in fluid communication with a motor driven pump to supply washing liquid under pressure to a spraying device that directs streams of washing liquid at dishes held in the washing chamber. As is known, the streams of washing liquid generally flow from one or more rotatable wash arms due to the effect of reactions caused by fluid jets coming out of respective pressure nozzles. It is also known to provide a dishwasher with fixed spray nozzle units.
Typically, the number of spray arms fed by a pump is limited by available water pressure in the dishwasher system. A drop in pressure within the system may reduce the intensity of the water jets, thus reducing cleaning power. Additionally, effective washing at the corners of a square wash rack is difficult to accomplish with standard spray arm configurations. In one proposed solution set forth in U.S. Patent Application Publication No. 2005/0011544, a dishwasher system allows a user to select particular quadrants of the dishwasher for more intense washing. More specifically, a control selectively operates a valve to block fluid to selected spray arms. Additionally, the speed of the circulating pump motor may be changed, thus altering the exit rate of water jets. However, such a system requires specific controls, and multiple supply lines to respective spray arms. Further, the rate of travel for a particular rotating arm is generally dictated by the pressure of the water jets issuing from the arms. Therefore, increasing the speed of the circulating pump not only increases water jet intensity, but reduces the dwell time, or the time water is impinging on articles in the dishwasher. Conversely, reducing the speed of the circulating pump decreases water jet intensity, but increases dwell time.
In any case, there is considered to be a need in the art for a dishwasher system having multiple wash arms for effective cleaning throughout a dishwasher, wherein the system allows for zone washing without sacrificing jet intensity or dwell time.